Powdered catalyst conversion



`lune 5, 1945. A. L. CONN l POWDERED CATALYST CONVERSION Filed Dec. 9, 1940 pnfyn N @www .QUT Nm ww PMUN EQ They may be discarded from the system by line l I4 andl employed for fuel oil purposes. However,

I prefer to increase the output of `gasoline from the system by recycling part or all oi' these heavy products through line 35 back to heater I2 wherein the heavy products, herein designated "recycle gas oil, are heated to a high conversion temperature and contacted with powdered catalyst.

In order to avoid dilculty with the recycle gas oil heater coil becoming stopped up with carbon,

I may discard all of the reflux condensate coli generator should be maintained below the point lected in the bottom of tower 28 and recycle only a gas oil fraction which is 4trapped out at a low point in the tower and recycled by line 33. I

'may also subject the recycle gas oil to selective extraction by a suitable solvent as indicated by the extraction stage 31 as shown in the drawing. Suitable valves in line 35 are indicated for bypassing part or all of the recycle stock through the extraction stage where the recycle stock is mixed with a selective solvent such as liquid sul 25 fur dioxide for removing aromatic constituents and thereby reducing the amount of carbon deposition occurring on the catalyst in the subsequent conversion reaction. Oil having an increased content of paraillnic hydrocarbons reilned by extraction in this way is conducted to the heater by line 33, while the extract fraction containing aromatic constituents is discarded by line 39.

After the recycle gas oil has been heated to the desired conversion temperature, for example, 950 to 10504 F., it is treated with catalyst in mixer and thence flows with the dispersed catalyst by line 4I to a third reaction chamber 42. This reaction chamberl may be provided with smaller- 40 contact space than either oi the preceding chambers, in order to avoid over-exposure of aromatic type hydrocarbon vapors to the catalyst. The rate of sedimentation of catalyst from the recycle gas oil vapors in chamber 42 may also be separately regulated by regulating the vapor velocity therein as indicated hereinabove with respect to reaction chambers 2i and 22. The temperature of the vapors in reaction chamber d2 will, in general, be higher than the temperature in reaction chambers 2i and 22. For example, it may be about 1000 F'. and generally Within the range of 950 to 1050 F.

The pressure employed in reaction chambers 2I, 22 and 42 is preferably atmospheric and gen- 55 erally not over 50 pounds per square inch. From reaction chamber 42 the converted vapors are passed by` lines 43 and 25 to cyclone separator 26 in admixture with the converted hydrocarbon vapors from the other reaction chambers of the system.

The used catalyst which is separated in separator 28 and collected in tower 21 is maintained at a high level within that tower in order to provide the necessary hydrostatic pressure in the base of the tower for recycling the catalyst. The catalyst in 21 is maintained in a free-flowing condition by introducing a stream of aerating gas through line 44 near the bottom of the tower.

It is desirable to use an inert gas, such as flue gas, etc., for this purpose. l('Jombustible gases and vapors are swept from the used catalyst, and

the gas may be conducted away by line Ma.

From the bottom of the used catalyst supply 21,

the catalyst is permitted to flow by a mechanical vlower temperaturel is advisable.

regulating device indicated o n the drawing by '.star valve 45, into vthe dispersing chamber 46 at which injury to the catalyst results. For certain synthetic silica catalysts and alumina-silica catalysts, temperatures of 1200 to 1900" F. may be allowable. With acid treated clays, however, and other catalysts such as magnesia-silica, a Temperatures below 1100 to 1200 F. are usually4 employed. The regenerator may alternatively comprise a vertical chamber with upwardly owing catalyst and regeneration gases.

From regenerator 49 the catalyst and regeneration gases are conducted by line 5I to cyclone separator 52 where the catalyst is separated and permitted to fall by gravity back to catalyst tower I1. Aerating gas introduced into tower I1 by line 53 assists in keeping the catalyst in free-flowing form in the tower I1. Inert gas or air may be used for this purpose. It is withdrawn at the top of the tower by line 54 leading to cyclone separator 52. Gas is separated in separator 52 or vented from the system by line 55.

I have found that it is generally desirable to employ steam Iadmixed with hydrocarbon vapors and catalyst in the reaction zones. For this purpose steam may be admixed by line 58 and directed intol any or all ofthe lines I0, II or 33 as desired. 'I'he mechanism of the action of steam in the reaction is not clearly understood 45 but it is believed to act on the catalyst in some character of carbon deposition on the catalyst surfaces.

Figure 2 illustrates a single reaction chamber which may be used in my process in place of reaction chambers 2|, 22 and 42. When using the reaction chamber 51, shown in Figure 2, lines i3, 20 and 4I are arranged to enter the reaction chamber at different levels to permit varying the reaction volume and indirectly the contact time for each type of stock. Thus, the light gas oil vapors in line I9 enter reaction chamber 51 at the base and travel throughout the full length of the reaction chamber until they are discharged by line 25 leading to cyclone separator 28. The heavy gas oil in line 20 and the recycle gas oil in line 4I enter the reaction chamber at successivelyl higher points. A series of inlets are connected by headers 58 and 59 to permit readily changing the points of introduction of the stocks. When using a single reaction chamber in this manner, instead of separate reaction chambers as shown in Figure 1, it is desirable to employ an elongated chamber with a relatively narrow cross sectional area to approach a streamline ow of the vapors through the reaction chambers and to avoid general mixing of the vapors which would result from counterflow. Longitudinal bailles, not shown, may also be employed to assist nemers' compositions may consist of 90 yto 98% of silica gel and the remainder promoting oxides. Other synthetic catalysts prepared by co-precipitatinsr silica and alumina'are eil'ective. Artificial zeolltes of various types may also be employed. Natural minerals may be used, including especially the clays, fullers earth, bentonite, bauxite, etc.,

, preferably activated by acid treatment. 'Ihe catalyst may be prepared in a fine state of subdivision by precipitation, for example, by adding ammonia to salt solutions to precipitate the hydrated. oxide or by adding acid to alkali salts such as sodium silicate, sodium aluminate, etc. Massive substances may be vilnely ground to the desited state of subdivision, for example. 100 mesh and finer. In general, the powdered catalyst which I employ will largely pass a 200 mesh screen and contain a very considerable portion passing 300 mesh and even `e130 mesh.

The ratio of catalyst to oil may vary depending on the activity of the catalyst, the stock treated, the conditions employed, etc. Ordiable.

narily, about 2 to 3 parts of catalyst per part of oil by weight is desirable. Under some condi-= tions I may use more or less catalyst, for example, from 1,/2 to l0 or 15 parts of catalyst per part oi oil -by weight. In general, the synthetic catalysts are more active than the natural catalysts and lower catalyst to oil ratios may be employed with them. lis an example of the ratio of catalyst to oil used for the different stocks, I may ernploy l to li pounds of catalyst per pound ci vcil for the light gas oil fraction, about V2 to 3 pounds of catalyst per pound of oil for the heavy gas oil fraction and about 5to 15 pounds of catalyst per pound ci recycle oil.

In catalytic cracking with the catalyst in a fixed bed it has been convenient to use the -space velocity as a measure of the severity of treatment from the catalyst standpoint. In general, the same catalyst will produce the same amount or gasoline from a charging stock under the same conditions of temperature and pressure if the space velocity is the same. The space velocity is commonly expressed `as the volume of liquid oil chargedper hour per unit volume of catalyst and for convenience the catalyst volume is usually taken as the .apparent volume of the catalyst when in compact form.

In the case of stationary bed catalysts, the space velocity is relatively easy to determine but in suspended catalyst operation with powdered catalysts, difficulties arise from the fact that the catalyst is not in compact form while in use and its volume is,- therefore, not directly determin- In powdered' catalyst operation, it is, therefore, more convenient to expresso space velocity on a weight basis as the pounds of oil per hour per pound of catalyst in the reaction zoneat l any given instant and the term mass velocity used herein shall be understood to have that meaning. This is readily determined from the rate of oil charged, the volume of the reaction chamber and the density of the catalyst in the reaction chamber. The density may be determined by the differential pressure between the top and the bottom of the reaction chamber, by

withdrawing and inspecting asample from the v reaction chamber or by other means. The ratio chamber.

oi fresh `catalyst to oil charged to the reaction chamber isimportant only as it afiects the catalyst residence time," i. e., the average time for particles oi catalyst to traverse the reaction This value may be readily calculated from the rates of charging catalyst and oil and the arnount'oi`l catalyst in the reaction chamber.

In generali-I employ a mass Vvelocity in the range of about 1 to 20 parts of oil per hour per part of catalyst by weight depending on the stock treated. A higher mass velocity may be desirable for the recycle gas oil converted in reaction chamber 42ior example, about 10 to 50. For the conversion di heavy gas oil in reaction chamber 22, I may suitably employ a, mass velocity of about 5 to 30 but for the conversion of light gas oil in chamber 2i. I usually employ a mass velocity of about 1 to 20. The choice of mass velocity employed within these ranges will depend on catalyst activity, the character of the oil treated, temperature oi the reaction zone and some other factors. In a typical example, zone 2i operates at t mass velocity, zone i2 at 8 mass velocity and zone 42 at 14 mass velocity. in general. the severity of cracking conditions lor each .stock in my process is controlled to effect optimum utilization of the catalyst rather than maximum conversion of hydrocarbons. l

I have described my invention Aby means of a specific method of its application. However, I do not intend that it be limited by method disclosed. For example, I have disclosed the use of reaction chambers of a specific type but I may also employ pipe coils for carrying out the reaction, the mixture of vapors and powdered catalyst being forced through coils 0i diderent lengths and volumes. Thus, l may use a long coil in place oi reactor il and shorter coils for reactors 22 and di, the desired reaction conditions being determined by the temperature at which the coils are maintained and by the volume of the coil.

Having thus described ,my invention, what I claim is;

l. The process of converting heavy hydrocarbon oils into gasoline oi high knock rating which comprises separately heating and vaporizing a plurality of streams of oil of different carbonization characteristics, dispensing powdered catalyst inthe resulting vapor streams, separately conducting said vapor streams and catalyst to separate reaction zones. withdrawing vapors and dispersed catalyst from said reaction zones, com bining the vapor-catalyst mixtures from said ren action zones, separating the combined catalyst from said vapors in a single separating zone, fractionating the separated vapors in a single fractionating zone and recovering a desired gaso line fraction therefrom, discharging separated combined catalyst to a single catalyst regenerating zone wherein carbonaceous deposits are removed by contacting with oxygen-containing gases, recycling and dispersing regenerated com bined catalyst in the vapor streams first mentioned and maintaining 'within said reaction zones different mass velocities to produce about the same amount of carbonaceous deposit on the catalyst in each of said reaction zones.

2. The process oi claim i wherein one of the oils charged to the system comprises heavier hy. drocarbons separated from gasoline ln said fractionating zone. l

3. The process oi claim l wherein two of the bien 4. avmors oils charged to the system comprise a light gas oil fraction and a heavy gas oil fraction obtained from the distillation of crude petroleum and said light gas oil is contacted with said catalyst at a lower mass velocity than said heavy Sas oil.

4. The process of claim i wherein a light gas oil and a heavy gas oil are charged to said reaction zones and the ratio of catalyst to oil suspended in the heavy sas oil reaction zone is substantially less than that in the light gas oil reaction zone.

5. The process of converting hydrocarbon oils into gasoline of high knock rating which comprises separating the oil vinto light and heavy fractions, heating said fractions in continuous streams to a high conversion temperature, continuously dispensing a powdered, solid catalyst in said vapor streams, separately conducting said vapor streams and dispersed catalyst to separate reaction zones, subjecting each of said vapor streams to catalytic conversion in said reaction zones at different mass velocities selected to produce about the same amount of carbonaceous deposit on the catalyst in each of said reaction zones, vcombining the said vapors and dispersed catalyst from said reaction zones in a. single catalyst separating zone, separating the combined catalyst from said vapors and regenerating it by combustion with oxygen-containing gases to remove carbonaceous deposits therefrom, redistributing combined regenerated catalyst between said light and heavy fractionsffractionating converted hydrocarbon vapors in a fractionating zone f and therein separating .the desired gasoline fraction from the heavier products of the conversion reaction.

6. The process of claim wherein the vproducts heavier than gasoline separated by said fractionating zone are subjected to extraction by a selective solvent, thereby increasing the concentration of parainic hydrocarbons in said heavier products and the treated heavier products are recycled to one of said separate catalytic reaction zones.

7. In the process of converting a heavy hydrocarbon oil into gasoline wherein said oil is continuously contacted with a powdered solid cracking catalyst at conversion temperatures in the range of 850 to 1050 F., the improvement comprising separating said heavy oil into a light and a heavy fraction, contacting said light fraction with suspended powdered catalyst in a rst reaction zone, contacting said heavy oil with said powdered catalyst in a second reaction zone, combining hydrocarbon vapors and catalyst from both reaction zones and separating the combined catalyst from said vapors in a catalyst separating zone, fractionating the separated vapors to produce'a desired gasoline fraction and a heavy lyst from said catalyst separating zone, regenerating it by controlled combustion with an oxygen-containing gas, distributing lthe regenerated combined catalyst among said reaction zones and regulating the conditions of temperature,

mass velocity and catalyst-tc-oil ratio in said reaction zones to eirect a substantially uniform deposit of carbon on said catalyst.

8. The process of claim 7 wherein said heavy recycle oil is extracted before recycling with a selective solvent to remove therefrom aromatic constituents.

9. The process of claim 7 wherein said light gas oil fraction is contacted in said first reaction zone at a mass velocity of about 1 to 20 pounds of oil per hour per pound of catalyst,

said heavy gas oil is contacted in said second reaction zone at a mass velocity of about 5 to 30 pounds of oil per hour per pound of catalyst and said heavy recycle oil fraction is contacted with catalyst in said third reaction zone at a mass velocity of about 10 to 50 pounds of oil per hour per pound of catalyst.

10. The process of converting heavy hydrocarbon oils into gasoline of high knock rating which comprises separately heating a plurality of streams of oil of different carbonization characteristics, separately conducting said heated streams to separate upfiow reaction zones wherein vaporous reaction products are produced, dispersing powdered catalyst in said upilow reaction zones, withdrawing vapors and dispersed catalyst from said reaction zones, combining the vapor-catalyst mixtures from said reaction zones, separating the combined catalyst from said vapors in a single separating zone, fractionating the separated vapors in a single fractionating zone and recovering the desired gasoline fraction therefrom, discharging separated combined catalysts to a single catalyst regenerating zone, wherein carbonaceous deposits are removed by contacting with oxygen-containing gases, recycling and dispersing regenerated combined catalyst in said upflow reaction zones, and maintaining within said reaction zones different mass velocities to produce about the same amount of carbonaceous deposit on the catalyst in each of said reaction zones.

ARTHUR L. CONN. 

